Fetch search result content

Retrieves selected results from a retained search. Provide exactly one of result_ids or limit; the latter fetches the top results. Content defaults to source:auto. Responses preserve result_ids order. Unknown result IDs are rejected before retrieval starts. Missing, expired, or inaccessible searches return 404. Once retrieval begins, return one outcome per selected result, including timeout entries for work unfinished at the overall deadline. Browser retrievals run sequentially in result order, so later results may time out when earlier pages are slow. X-Request-Id identifies this request separately from the search resource.